An inquiry has begun after a 75-year-old man collapsed in a police station and later died.
The man collapsed at 1810 GMT on Wednesday while in Chesterfield police station.
Efforts were made to resuscitate the man but he died three hours later after undergoing emergency surgery at Queen's Medical Centre in Nottingham.
The man, who has not been named by police, had gone to the station voluntarily in connection with an investigation.
The Police Complaints Authority (PCA) will oversee an investigation into the circumstances of his death.
A PCA spokesman said: "Derbyshire Constabulary immediately asked PCA member Anne Boustred to supervise the investigation that they are carrying out."
He said a post-mortem examination was being carried out by a Home Office pathologist on Thursday.